Accurate diagnosis of a watered zone (also referred to as water exploration test in the industry) is the base and key for water control and stabilizing oil production in a horizontal well with high watercut problem, and is also a long-standing problem in production and management of a horizontal well both at home and abroad. At the present stage, the diagnosis of a watered zone can only rely on a foreign wireline logging method by using “downhole tractor+holdup meter+multi-parameter instrument”. However, through application it is found that this method has the disadvantages that the wireline cannot go down along a complex drilling trajectory, and cannot pass through a complex well bore in a horizontal well, the logging cost thereof is high, the method cannot be applied on a large scale, the application scope is not wide, and the like. In addition, due to great difficulty in the process of construction and high risk in the process of operation, a number of horizontal wells with high watercut problem, with the long-standing problems of water producing unresolved, have to work in poor conditions and are even shut down and abandoned, which leads to extremely serious economic loss.